1. Field of the Invention
The present invention relates to a signal processing system of an image pickup device which reads an image signal from a high resolution image pickup device in a form compatible to a broadcast television signal system to permit monitoring, recording and reproducing a still image.
2. Related Background Art
A conventional solid-state image pickup device such as a CCD usually has several hundred thousands effective pixels. With a solid-state image pickup device having such a number of pixels, the device is read with sampling at a horizontal scan frequency of broadcast television with 2-to-1 interlace. Accordingly, the signal can be reproduced as it is on a general purpose television monitor and recorded onto a VTR or a floppy disk developed for an electronic still camera.
Recently, a high resolution image pickup device (approximately 1,200,000 pixels) having vertical effective pixels double the number of effective horizontal scan lines of broadcast television has been put into practical use. In the signal processing of such a high resolution image pickup device, if the 2-to-1 interlace system is used, a image pickup device is read at the horizontal scan frequency double the horizontal scan frequency of the broadcast television. As a result, the number of horizontal scan lines is different from that of the existing broadcast television system, and the output image must be watched by a special television monitor which is compatible to the drive system of the high resolution image pickup device. A special equipment is also required to record and reproduce the image signal.
Since the signal processing system of a high resolution image pickup element which is not compatible to the existing broadcast television signal system requires special monitor and recording/reproducing apparatus, the circuit configuration is complex, the apparatus is bulky, and the cost increases. Accordingly, it has been difficult to conveniently use the high resolution image pickup device.